fungi Flashcards
what is mycosis?
infections caused by fungi
mycosis = in humans and other animals, an infection caused by any fungus that invades the tissues, causing superficial, subcutaneous, or systemic disease.
describe the structure of fungi cels
Eukaryotic
Chitinous cell wall
how do fungi spread/move?
Move by means of growth or through the generation of spores, which are carried through air or water
what are yeasts?
Yeasts are small single celled organisms that divide by budding
type of fungi
what are moulds?
type of structure fungi can form
forms from multicellular hyphae (branching structures) and spores
what are moulds?
type of fungi
what are dimorphic fungi?
fungi that exist as both yeasts and mould, s switching between the two when conditions suit
why do fungi struggle to affect humans ie. to cause human mycoses ?
Can’t grow at 37 degrees
Can’t evade our immune responses
which is more common? a superficial or invasive fungal disease?
Superficial fungal infection → very common
Invasive fungal infection → rare but easily missed
Examples of common but mild fungal infections:
Nappy rash
Vulvovaginal candidiasis (thrush)
Tinea pedis (athlete’s foot)
Onychomycosis (fungal nail infections)
Otitis externa
Fungal asthma
Examples of life threatening fungal disease:
In Immunocompromised hosts
Candida line infections (IV lines)
Invasive aspergillosis (a common mould, breathed in by most people without getting ill)
Pneumocystis
Cryptococcosis
Mucormycosis
Example of life threatening fungal disease:
Post-surgical patients
intra-abdominal infection
Example of life threatening fungal disease:
healthy hosts
Fungal asthma
Travel associated fungal infections
Dimorphic fungi
Post-influenza aspergillosis
what are often the drawbacks of fungal diagnostic techniques?
often insensitive in early stages of infection
can be poorly specific
work well for yeasts and less well for moulds eg. culture
have to request them specifically
list some diagnostic techniques to identify fungi
radiology
microscopy
culture
PCR tests
antigen tests
fungal disease treatment work via selective toxicity
what is meant by selective toxicity?
Aim of antimicrobial drug therapy is to achieve inhibitory levels of agent at the site of infection without host cell toxicity
Fungi can be challenging to treat as we have relatively few classes of agent effective against them
name the drug that used to be the mainstay treatment for fungal disease treatment ?
Amphotericin B
how does Amphotericin B work and why is it no longer preferred as treatment for fungal infections?
Forms a pore in the membrane, disrupts membrane proteins
Used to be mainstay drug, is very broad spectrum with a high barrier to resistance
but:
- IV only
- Has significant Adverse effects
name a commonly used treatment for candida fungi
what is its drawback?
Echinocandins
Iv only
what drugs are the current mainstay antifungal therapy?
Azoles
eg. fluconazole
Azoles are relatively safe drugs however they do have what potential adverse effects with long term use?
- hepatitis
- alopecia
- GI symptoms eg. abdominal pain
- visual disturbance
Azoles are relatively safe drugs however they do have several drug-drug interactions to be aware of
Interfere with metabolism of other drugs, and other drugs can interfere with azole metabolism , largely as a result of cytochrome P450 isoforms
list some key interactions
fluconazole
- interacts with Warfarin
itraconazole
- interacts with statins and steroids
what fungi causes infections of toenails
onychomycosis
Caused by dermatophyte moulds
what does it mane if a test comes back Beta-D-glucan positive
Beta-D-glucan is a cell wall component of many fungi
therefore this result shows a fungi is present
is a non-specific result
